First off I am High Functioning and this also includes examples of 2 friends of mine (who are likewise). By High Functioning in the context of this post I mean folks who are 1) Mentally Disabled 2) Generally don't qualify or get SSDI and need work to live 3) Able to otherwise live mostly to fully independently.
So I want to knock out right off the bat that yes there ARE laws that protect us, however alot of the tactics you will hear about here fall where discrimination based on ADA (Americans with Disabilities Act) may be difficult to impossible to prove yet the similarities that occur show that yes this is indeed happening to disabled people.
For me I've been working for around 14 years now, had several jobs and despite several of them were I was top performer I've been given little opportunity to the point that as of this post I've only been promoted 1 time so far at a job (namely cuz my friend, not the ones being mentioned later, was 2nd in command and vouched / pushed for me to be placed in a higher position.) and the best I had gotten before that was an interview where they knew or had offered the position but needed to fill a quota for interviews. I would always express interest in learning things so I could move up and in my current position am as knowledgeable as the supervisors and even some of the managers. Despite this I've had concerns over “stress” be used an an excuse and one were a struggle to learn something was used against me (knowing full well my disability)
For my 2 friends I should mention neither drives which has been a source of Shenanigans used against them such as Scheduling them after the local buses are done for the night or before they start despite knowing they cannot drive and rely on buses / mass transit to get to work and back and has been used to force them out by doing hours that wouldn't work for them. This is before Uber / Lyft etc also were commonplace as well and even so today such services would be too costly when you re working low wage jobs.
At my current job I am entry level yet know as much as the supervisors / managers and never have been asked if I were even interested in promotion when positions became available. One of my friends did reach a supervisor level position only to be forced out within a month or 2 of that.
At one job I worked there was another individual who I suspect was disabled like me and both of us were timed on tasked (no one else otherwise was) and generally singled out by our supervisor.
I don't think that people understand that some of us who do work low wage jobs do so because we are not given anything near the same level of opportunities as our peers are, despite we might be harder working or in some cases being as or more knowledgeable than our peers.
Also I've done programs from both non profit and county government (voc. rehab) and they focus more on just getting you into a job and let you go after you show you can stay in it, so far as I know there are not really any organizations that focus on growing at a job, which is not very helpful for high functioning people who are capable.
If you are a supervisor / manager I would ask you give your disabled employees the opportunities you give others
If you are concerned by this then contact your state / federal lawmakers and ask for more to be done for those in the position this sort of situations. I'm not asking to change the world here, just that we get a chance, and opportunity and not tosses aside because of our disability..